Hand-Held Machine Tool

ABSTRACT

The disclosure relates to a hand-held machine tool, comprising a drive unit, a gearbox unit, which comprises at least one input shaft and at least one output shaft operatively connected to the input shaft, and a tool holder, which is configured to be driven via the output shaft of the gearbox unit in an oscillating manner about an axis of rotational symmetry of the output shaft. A vibration compensating unit is proposed, which comprises at least one compensating mass which, in order to compensate for a vibration, is driven in at least one operating state against a direction of movement of the tool holder.

PRIOR ART

The invention is based on a hand power tool according to the preamble ofclaim 1.

There are already known hand power tools comprising a drive unit, atransmission unit, which has at least one input shaft and at least oneoutput shaft that is operatively connected to the input shaft, andcomprising a tool receiver, which can be driven in an oscillatingmanner, via the output shaft of the transmission unit, about arotational symmetry axis of the output shaft.

DISCLOSURE OF THE INVENTION

The invention is based on a hand power tool comprising a drive unit, atransmission unit, which has at least one input shaft and at least oneoutput shaft that is operatively connected to the input shaft, andcomprising a tool receiver, which can be driven in an oscillatingmanner, via the output shaft, about a rotational symmetry axis of theoutput shaft.

It is proposed that the hand power tool has a vibration compensatingunit, which has at least one compensating mass that, for the purpose ofcompensating a vibration, in at least one operating state, is drivencontrary to a direction of motion of the tool receiver. A “compensatingmass” is to be understood to mean a component provided to compensatevibrations, at least partially, preferably fully, in an operating state.“Vibrations” are to be understood to mean, in particular, unwantedmotions of the hand power tool that are caused, in particular, bymoments of inertia produced by an oscillating motion. The compensatingmass according to the invention enables vibrations to be reduced,preferably reduced to zero, when the hand power tool is in an operatingstate. As a result, advantageously, comfort in operation of the handpower tool can be increased for a user. In addition, noises resultingfrom unwanted vibrations when the hand power tool is in an operatingstate can be advantageously reduced, such that, particularlyadvantageously, the operating comfort can be increased for the user. Inaddition, the reduction of the vibrations, in particular the reductionof the vibrations to zero, makes it possible to achieve anadvantageously precise working result when the hand power tool is in anoperating state.

Further, it is proposed that the transmission unit has at least onefirst cam mechanism, which is provided to drive the tool receiver, andhas at least one second cam mechanism, which is provided to drive thecompensating mass. A “cam mechanism” is to be understood to mean, inparticular, a mechanism by which a shape of a moving curve is picked upby a feeler and transmitted to a further transmission element such as,for example, to the output shaft. Particularly preferably, the cammechanism has at least one eccentric element. In this context, an“eccentric element” is to be understood to mean a component, inparticular a disk-shaped component, whose center point, and preferablyalso whose center of gravity are disposed so as to be spaced apart froma rotation axis of the component. A “disk-shaped component” is to beunderstood to mean, in particular, a component whose material extent inthe radial direction is at least 10% of a diameter of the component, anaxial extent of the component preferably being less than 10% of thediameter.

Owing to the first and the second cam mechanism, a rotary motion of thedrive unit can be easily converted into an oscillating motion. Inaddition, advantageously, the transmission unit according to theinvention can be designed in an inexpensive and particularly robustmanner.

If the first cam mechanism and the second cam mechanism are operativelycoupled to the drive unit, the drive unit can drive the first and thesecond cam mechanism. Consequently, only one drive unit is required togenerate two motions, in particular two mutually opposing motions, oftwo components that differ from each other. Advantageously, it isthereby possible to save structural space, with the result that the handpower tool can be designed, particularly advantageously, to be small andeasy to manipulate.

In addition, it is proposed that a first eccentric element of the firstcam mechanism and a second eccentric element of the second cam mechanismare disposed on the input shaft. Since the first eccentric element ofthe first cam mechanism and the second eccentric element of the secondcam mechanism are disposed on the input shaft, an advantageously compactstructural design can be achieved. Also conceivable, however, asalternatives or in addition to the cam mechanisms constituted byeccentric elements, are other cam mechanisms, considered appropriate bypersons skilled in the art, for converting a rotary motion into anoscillating swivel motion.

In a further design of the invention, it is proposed that the eccentricelements are offset in relation to each other by at least substantially180°. In this context, “at least substantially 180°” is to be understoodto mean that a first straight line through the center point of the firsteccentric element and through the rotation axis of the input shaft,which straight line runs perpendicularly in relation to a rotation axisof the input shaft, and a second straight line through the center pointof the second eccentric element and through the rotation axis of theinput shaft, which straight line runs perpendicularly in relation to therotation axis of the input shaft, enclose an angle that, in particular,is less than 20°, preferably less than 10°, particularly preferably lessthan 5°, the center points of the first and the second eccentricelements being disposed, in a radial direction of the input shaft, onmutually at least substantially opposite sides of the input shaft. In aparticularly advantageous design, the first and the second straight lineare disposed parallelwise in relation to each other, the center pointsof the first and the second eccentric element being disposed, in theradial direction of the input shaft, on mutually opposite sides of theinput shaft. The disposition, according to the invention, of the firstand the second eccentric element enables an imbalance of the first andthe second eccentric element to be compensated in an advantageouslysimple manner.

It is proposed that the hand power tool has an angled motion converter,via which the compensating mass of the vibration compensating unit isoperatively connected to the second cam mechanism. In this context, a“motion converter” is to be understood to mean a component provided toconvert a rotary motion of the drive unit into an oscillating motion ofthe compensating mass about the rotational symmetry axis of the outputshaft. “Angled” is to be understood to mean, in particular, a change inthe direction of extent of between 45° and 135°, preferably of between70° and 110°, and particularly preferably of 90°. The design, accordingto the invention, of the angled motion converter enables the motionconverter to be realized, advantageously, in a space-saving manner and,consequently, an advantageously compact structural design of thetransmission unit can be achieved.

It is proposed that the compensating mass of the vibration compensatingunit and the angled motion converter are realized in an at leastpartially integral manner. “Integral” is to be understood to mean, inparticular, connected by material bonding such as, for example, by awelding process and/or adhesive bonding process, etc. and, particularlyadvantageously, formed-on, such as being produced from a casting and/orbeing produced by a single-component or multi-component injectionmolding method. Preferably, owing to the integral design of the motionconverter and of the compensating unit, savings in components can bemade, and as a result, advantageously, an assembly process can besimplified.

It is further proposed that the compensating mass of the vibrationcompensating unit is rotatably mounted on the output shaft. This makesit possible to achieve a reduction in vibrations in an advantageouslyeffective and, at the same time, simple manner, in particular thereduction of vibrations to zero, when the hand power tool is in anoperating state, thereby advantageously enabling the operating comfortfor the user to be increased.

DRAWING

Further advantages are given by the following description of thedrawing. The drawing shows an exemplary embodiment of the invention. Thedrawing, the description and the claims contain numerous features incombination. Persons skilled in the art will also expediently considerthe features individually and combine them to create appropriate furthercombinations.

In the drawing:

FIG. 1 shows a perspective side view of a hand power tool according tothe invention,

FIG. 2 shows a schematic sectional representation of a partial region ofthe hand power tool with a transmission unit according to the inventionand with a portion of a drive unit,

FIG. 3 shows a schematic sectional representation of the transmissionunit of the hand power tool according to the invention, along the lineIII-III, and

FIG. 4 shows a schematic sectional representation of the transmissionunit of the hand power tool according to the invention, along the lineIV-IV.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

FIG. 1 shows a hand power tool, which can be driven in an oscillatingmanner and which has a switch 38, for switching the hand power tool onand off, integrated into a housing 36 of the hand power tool that servesas a handle. Disposed in a front region of the hand power tool is a toolreceiver 18, with an insert tool 40 held therein. In addition, the handpower tool comprises a drive unit 10, constituted by an electric motor,not represented in greater detail, and a transmission unit 12. In aregion that faces away from the tool receiver 18 in a direction of mainextent 42 of the hand power tool, the hand power tool has an electricpower cable 44 for supplying electric power to the drive unit 10.

The transmission unit 12 of the hand power tool is represented ingreater detail in FIG. 2. The transmission unit 12 has an input shaft14, which can be driven in rotation by means of the drive unit 10 andwhich is operatively connected to a first and a second cam mechanism 30,32. The first cam mechanism 30 has a first eccentric element 31, whichis pressed on to a free end of the input shaft 14. The second cammechanism 32 has a second eccentric element 33, which likewise ispressed on to the input shaft 14. The eccentric elements 31, 33 areidentical in their structural design and are disposed with an offset of180°, such that a center of gravity S₁ of the first eccentric element31, corresponding to a center point of the first eccentric element 31,and a center of gravity S₂ of the second eccentric element 33,corresponding to a center point of the second eccentric element 33, aredisposed in series in a radial direction 46 of the input shaft 14. Thefirst eccentric element 31 is operatively connected to an output shaft16 of the transmission unit 12 via a first motion converter 48configured in a level manner. “Configured in a level manner” is to beunderstood to mean, in particular, that the first motion converter 48extends, at least substantially, in a plane disposed parallelwise inrelation to the input shaft 14 of the drive unit 10 and perpendicularlyin relation to the output shaft 16 of the transmission unit 12. “Atleast substantially” in this case is to be understood to mean, inparticular, that the first motion converter 48, with the plane, enclosesan angle that, in particular, is less than 15°, particularly preferablyis less than 5°. In this exemplary embodiment, the first motionconverter 48 is parallel to the plane.

The first motion converter 48 has a first region 50 that faces towardthe insert tool 40 in the direction of main extent 42 of the hand powertool and that has a circular recess 52, into which the output shaft 16is pressed. Furthermore, the first motion converter 48 has a secondregion 54, which extends, from an end of the first region 50 that facesaway from the insert tool 40, in the direction of main extent 42, to thedrive unit 10. The second region 54 of the first motion converter 48 hastwo arms 56. Ends of the arms 56 of the second region 54 of the firstmotion converter 48 that face toward the drive unit 10 engage, onopposing sides of the first eccentric element 31, on a circumferentialsurface 58.

The output shaft 16 of the transmission unit 12 extends, perpendicularlyin relation to the direction of main extent 42 of the hand power tool,as viewed from the first motion converter 48, toward the tool receiver18. The output shaft 16 is mounted by two bearings 62, 64 so as to berotatable relative to the housing 36 of the hand power tool. The toolreceiver 18 is disposed on an end of the output shaft 16 that faces awayfrom the first motion converter 48. The tool receiver 18 comprises aseating flange 66, which is pressed on to the output shaft 16 and onwhich the insert tool 40 is seated when in a mounted state. In addition,the tool receiver 18 comprises a fastening screw 68, which, extendingthrough the insert tool 40, is screwed into a threaded bore, notrepresented in greater detail, in the output shaft 16. When in a mountedstate, a screw head 70 of the fastening screw 68 is supported, inrespect of the insert tool 40, on a washer 72. When in a mounted state,the insert tool 40 fixes positively relative to the output shaft 16.

A second motion converter 34, which has an angled configuration, engageson the second eccentric element 33. The second motion converter 34 isconfigured with a 90° angle, and comprises a first region 74 and asecond region 76. The first region 74 of the second motion converter 34is disposed parallelwise in relation to the input shaft 14 and isconnected to a vibration compensating unit 20. The second region 76 ofthe second motion converter 34 adjoins an end of the first region 74that faces away from the output shaft 16, and extends, parallelwise inrelation to the output shaft 16, in an axial direction 60 of the outputshaft, toward the input shaft 14. The second region 76 of the secondmotion converter 34 has two arms 78, the free ends of which, facingtoward the input shaft 14, engage on opposing sides of a circumferentialsurface 80 of the second eccentric element 33.

The vibration compensating unit 20 is constituted by a compensating mass22 that is realized so as to be integral with the second motionconverter 34 and disposed so as to be rotatable about the output shaft16. A center of gravity S₃ of the compensating mass 22 is disposed on aside of the output shaft 16 that faces toward the drive unit 10, in aradial direction 82 of the output shaft. A center of gravity S₄ of theinsert tool 40 is disposed on the side of the output shaft 16 that isopposite the center of gravity S₃ of the compensating mass 22, in theradial direction 82 of the output shaft 16.

When the hand power tool is in an operating state, the input shaft 14,and the eccentric elements 31, 33 disposed on the input shaft 14, aredriven in rotation by the drive unit 10. The eccentric motion of thefirst eccentric element 31 is taken up by the first motion converter 48in a plane in which a rotational symmetry axis of the input shaft 14 islocated, and which is perpendicular to the output shaft 16. Theeccentric motion of the second eccentric element 33 is taken up by thesecond motion converter 34 in a plane that extends parallelwise inrelation to the direction of main extent 42 of the hand power tool andthat is perpendicular to the output shaft 16. Produced as a result is anoscillating motion 28 of the first and the second motion converter 34,48 about an axis that corresponds to a rotational symmetry axis 84 ofthe output shaft 16.

The oscillating motion 28 of the first motion converter 48 istransmitted, via the output shaft 16, to the tool receiver 18 and to theinsert tool 40 held therein. The oscillating motion 28 of the secondmotion converter 34 is transmitted to the compensating mass 22, which isintegrally connected to the second motion converter 34 and rotatablymounted on the output shaft 16 of the transmission unit 12.

Owing to the phase displacement of the oscillating motions 28 of thefirst and the second motion converter 34, 48, or of the tool receiver 18and the compensating mass 22, vibrations that are caused by moments ofinertia produced by an oscillating motion 28 of the insert tool 40 whenthe hand power tool is in an operating state are compensated by thecompensating mass.

FIG. 3 shows a sectional view along the line III-III. The centers ofgravity S₁ and S₂ of the eccentric elements 31, 33, when in the positionshown, lie on a straight line that is perpendicular to the direction ofmain extent 42 and parallel to the axial direction 60. The arms 56 ofthe first motion converter 48 bear against opposing sides of acircumferential surface 58 of the first eccentric element 31 in theradial direction 46 of the input shaft 14. The arms 78 of the secondmotion converter 34 bear against the circumferential surface 80 of thesecond eccentric element 33 in the radial direction 46 of the inputshaft 14.

FIG. 4 shows a portion of the hand power tool, in a section along theline IV-IV. The first motion converter 48 comprises the first region 50having the recess 52, and comprises the second region 54 having the twoarms 56. The ends of the arms 56 engage on the circumferential surface58 of the first eccentric element 31, which is represented in section.The ends of the arms 78 of the second motion converter 34 engage on thecircumferential surface 80 of the second eccentric element 33, which islikewise represented in section.

When the hand power tool is in an operating state, a rotary motion 26 ofthe drive unit 10 and of the input shaft 14 driven by the drive unit 10is transmitted to the first and the second eccentric element 31, 33 thatare pressed on to the input shaft 14. The first and the second eccentricelement 31, 33 in this case describe an orbit, which is other than acircle, about a rotational symmetry axis 86 of the input shaft 14. Theends of the arms 56, 78 of the first and the second motion converter 34,48 each respectively take up a component of the non-circular motion ofthe first and the second eccentric element 31, 33 in a direction that isperpendicular to the direction of main extent 42 of the hand power tooland perpendicular to the axial direction 60 of the output shaft 16. Inthis context, “non-circular” is to be understood to mean, in particular,being at least substantially different from a circle. This component ofthe non-circular motion of the eccentric elements 31, 33 causes anopposing oscillating motion 28 of the first and the second motionconverter 34, 48 about the rotational symmetry axis 84 of the outputshaft 16.

The oscillating motion 28 of the first motion converter 48 istransmitted to the output shaft 16 pressed into the recess 52, and tothe insert tool 40 that is fastened to the output shaft via the toolreceiver 18. The oscillating motion 28 of the second motion converter 34is transmitted to the compensating mass 22 of the vibration compensatingunit 20 that is integrally formed on to the second motion converter 34.

1. A hand power tool comprising: a drive unit; a transmission unitincluding (i) at least one input shaft and (ii) at least one outputshaft operatively connected to the input shaft; a tool receiverconfigured to be driven in an oscillating manner, via the output shaftof the transmission unit, about a rotational symmetry axis of the outputshaft; and a vibration compensating unit including at least onecompensating mass that, in at least one operating state, is configuredto be driven contrary to a direction of motion of the tool receiver,wherein the vibration compensation unit is configured to compensate avibration.
 2. The hand power tool as claimed in claim 1, wherein thetransmission unit includes (i) at least one first cam mechanismconfigured to drive the tool receiver, and (ii) at least one second cammechanism configured to drive the compensating mass.
 3. The hand powertool as claimed in claim 2, wherein the first cam mechanism and thesecond cam mechanism are operatively coupled to the drive unit.
 4. Thehand power tool as claimed in claim 3, wherein: the first cam mechanismincludes a first eccentric element disposed on the input shaft, and thesecond cam mechanism includes a second eccentric element disposed on theinput shaft.
 5. The hand power tool as claimed in claim 4, wherein thefirst eccentric element and the second eccentric element are offset inrelation to each other by at least substantially 180°.
 6. The hand powertool as claimed in claim 2, further comprising: an angled motionconverter configured to operatively connect the compensating mass of thevibration compensating unit to the second cam mechanism.
 7. The handpower tool as claimed in claim 6, wherein the compensating mass of thevibration compensating unit and the angled motion converter are realizedin an at least partially integral manner.
 8. The hand power tool asclaimed in claim 1, wherein the compensating mass of the vibrationcompensating unit is rotatably mounted on the output shaft.